With the development of modern society, users' preference of portable electronic devices has increased and the electronic devices have become essential for providing a uniquitous environment to users. Various electronic devices which currently support communication functions now move from a communication scheme using a wired cable, such as a telephone line, a network cable, a headphone cable, etc. to a communication scheme using wireless technology, such as Bluetooth, a wireless Local Area Network (LAN), etc. At present, power supply to portable electronic devices is mostly managed by rechargeable batteries, and therefore, the introduction of wireless charging to the field of battery charging may be innovative.
The wireless charging technology is also called wireless power technology in which for example, a battery of an electronic device is charged once the electronic device is put on a charge pad, instead of being connected to a separate charge connector. Generally, a battery of a wireless electric toothbrush or a wireless shaver is charged using the wireless charging technology, which is also known to the public. This technology may improve a waterproof function in a sense that an electronic product is wirelessly charged, and may also improve portability of the electronic product because of not requiring a wired charger.
The wireless charging technology may be roughly classified into an electromagnetic induction scheme using coils, a wireless power transmission scheme which converts an electric energy into microwaves for transmission, and a scheme using resonance. The wireless charging technology will be described in more detail below.
The electromagnetic induction scheme transmits power between a primary coil and a secondary coil. The movement of a magnet in a coil generates induced current, thus generating electricity. That is, a transmission unit generates a magnetic field, such that current is induced according to a change of the magnetic field in a reception unit, thus producing energy. A phenomenon in which current is generated by a coil and a magnet is called a magnetic induction phenomenon. The electromagnetic induction scheme is advantageous in its high energy-transmission efficiency, such that this scheme has been commercialized most in the wireless charging technology, and has been applied to various electronic devices.
The scheme using resonance wirelessly transmits power by using a resonance-based power transmission principle, even when a charging device is located several meters away from an electronic device. This scheme uses the physics concept of resonance in which if a tuning fork is hit, a wine glass near the tuning fork vibrates at the same frequency of the tuning fork. Electromagnetic waves, instead of sound, containing electric energy are resonated to wirelessly transmit power.
The wireless power transmission scheme radiates Radio Frequency (RF)/microwaves to wirelessly transmit power. This scheme is a new concept of power transmission which converts power energy into microwaves favorable to wireless transmission and transmits energy.
An internal structure of an electronic device using the above-described wireless charging technology will be described in detail.
FIG. 1 is a block diagram illustrating an internal structure of a conventional electronic device which is wirelessly rechargeable. In FIG. 1, an electronic device 11 which transmits power and an electronic device 12 which receives power are shown together.
Referring to FIG. 1, the power-transmitting electronic device 11 may include a power conversion unit 101, a communication and control unit 103, and a coil 105. The power conversion unit 101 is connected with the coil 105 for generating a magnetic field, and the communication and control unit 103 controls the power conversion unit 101 to supply power up to a level desired by the power-transmitting electronic device 11.
The power-receiving electronic device 12 may include a coil 107, a power reception unit 109, a communication and control unit 111, and a battery 113. The power reception unit 109 is connected with the coil 107 for power supply and demand. The communication and control unit 111 controls power supplied by the power-transmitting electronic device 11 to the battery 113.
The power-transmitting electronic device 11 shown in FIG. 1 is typically a charging pad, and the power-receiving electronic device 12 is a portable electronic device having a rechargeable battery, such as a mobile terminal. Generally, in the course of wireless charging, a Light Emitting Diode (LED) indication lamp of the power-transmitting electronic device 11 or the power-receiving electronic device 12 is flickered or lighted, and upon completion of wireless charging, the LED indication lamp thereof is lighted in green, as shown in FIGS. 2 and 3.
FIGS. 2 and 3 are diagrams illustrating a conventional wireless charging system. In the system illustrated in FIGS. 2 and 3, a power-transmitting electronic device is a charging pad 201 and a power-receiving electronic device is a portable mobile terminal 203. FIG. 2 shows a state in which wireless charging is in progress, and FIG. 3 shows a state in which wireless charging is completed.
Referring to FIG. 2, once the portable mobile terminal 203 is put on the charging pad 201, wireless charging starts. When wireless charging starts, an LED indication lamp 205 of the portable mobile terminal 203 is flickered or lighted in red to inform a user that wireless charging is in progress.
Referring to FIG. 3, after an elapse of a predetermined time since the portable mobile terminal 203 has been put on the charging pad 201, wireless charging is completed. Upon completion of wireless charging, the LED indication lamp 205 of the portable mobile terminal 203 is flickered or lighted in green to inform the user that wireless charging has been completed.